'\"
'\" Copyright (c) 2009 by Kevin B. Kenny.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
.TH Tdbc_Init 3 8.6 Tcl "Tcl Database Connectivity"
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.BS
.SH "NAME"
Tdbc_Init, Tdbc_MapSqlState, Tdbc_TokenizeSql \- C procedures to facilitate writing TDBC drivers
.SH SYNOPSIS
.nf
\fB#include <tdbc.h>\fR

int
\fBTdbc_Init\fR(\fIinterp\fR)

Tcl_Obj *
\fBTdbc_TokenizeSql\fR(\fIinterp, sqlcode\fR)

const char *
\fBTdbc_MapSqlState\fR(\fIstate\fR)
.fi
.SH ARGUMENTS
.AS "Tcl_Interp" statement in/out
.AP Tcl_Interp *interp in/out
Pointer to a Tcl interpreter.
.AP "const char" *state in
Pointer to a character string containing a 'SQL state' from a database error.
.AP "const char" *sqlcode in
Pointer to a character string containing a SQL statement.
.BE

.SH DESCRIPTION
.PP
The TDBC library provides several C procedures that simplify writing a TDBC
driver. They include a procedure that tokenizes a SQL statement, locating
variables to be substituted, and a procedure that accepts a SQL state and
returns an error class for the interpreter error information.
.PP
\fBTdbc_Init\fR must be invoked prior to any other TDBC call.  It accepts
a pointer to a Tcl interpreter, and arranges to load the TDBC library. It
returns \fBTCL_OK\fR if the Tcl library was loaded successfully, and
\fBTCL_ERROR\fR otherwise. If \fBTCL_ERROR\fR is returned, the
interpreter's result contains the error message.
.PP
\fBTdbc_TokenizeSql\fR accepts a pointer to a Tcl interpreter, and a
pointer to a character string containing one or more SQL
statements. It tokenizes the SQL statements, and returns a pointer to
a Tcl_Obj that contains a list of the tokens that make up the
statement. Concatenating the tokens together will yield the original
SQL code. The returned Tcl_Obj has a reference count of zero. The
caller is responsible for managing the reference count as needed.
See \fBTOKENS\fR below for a description of what may be in the
returned list of tokens.
.PP
\fBTdbc_MapSqlState\fR accepts a pointer to a string, usually five
characters long, that is the 'SQL state' that resulted from a database
error. It returns a character string that is suitable for inclusion as
the error class when constructing the error code for an error in a
TDBC driver. (By convention, the error code is a list having at least
four elements: "\fBTDBC\fR \fIerrorClass\fR \fIsqlstate\fR
\fIdriverName\fR \fIdetails...\fR".)
.SH TOKENS
Each token returned from \fBTdbc_TokenizeSql\fR may be one of the
following:
.IP [1]
A bound variable, which begins with one of the 
characters '\fB:\fR', '\fB@\fR', or '\fB$\fR'. The 
remainder of the string is the variable
name and will consist of alphanumeric characters and underscores. (The
leading character will be be non-numeric.)
.IP [2]
A semicolon that separates two SQL statements.
.IP [3]
Something else in a SQL statement. The tokenizer does not attempt to
parse SQL; it merely identifies bound variables (distinguishing them
from similar strings appearing inside quotes or comments) and
statement delimiters.
.SH "SEE ALSO"
tdbc(n), tdbc::mapSqlState(n), tdbc::tokenize(n)
.SH "KEYWORDS"
TDBC, SQL, database, tokenize
.SH "COPYRIGHT"
Copyright (c) 2009 by Kevin B. Kenny.
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